Well bore casing releasing apparatus



Sept. 14, 1965 Q c, PRESTON, JR 3,205,948

WELL BoRE cAsING RELEASING APPARATUS Filed April 5, 1962 5 Sheecs--Shei'l 1 pim. I. F26. 2.

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Sept. 14, 1965 D.y c. PRESTON, JR

WELL BORE CASING RELEASING APPARATUS 5 Sheets-Sheet 2 Filed April 5, 1962 INVENTOR.

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MMM/MM #rra/@Mex Sept. 14, 1965 D. c. PRESTON, JR 3,205,948

WELL BORE CASING RELEASING APPARATUS Filed April 5, 1962 s sheets-sheet s E60 D .F260 5&0

INVEN TOR.

3,205,948 WELL BURR CASING RELEASING APPARATUS Dan C. Preston, r., Whittier, Edif., assignor to Baiser @il Tools, Inc., Los Angeles, Caiit., a corporation ot Caliir'ornin Filed Apr. S, 1962, Ser. No. 185,393

13 Claims. (Ci. 166-225) The present invention relates to`subsurface well bore apparatus, and more particularly to subsurface apparatus for releasably interconnecting upper and lower portions of well casing, or similar conduit string, in well bores.

In some well bores, a casing string has been lowered through a producing Zone in a well bore and cemented in the well bore both above and below the producing Zone. After cementing the casing string in the well bore, the section of casing opposite the producing Zone has been milled out, after which a hole enlarging tool has been used to fully expose the producing Zone.

It has been proposed to avoid the milling out and hole enlarging operations by running the casing in the well bore, depositing cement around a lower portion of the casing below the producing zone, releasing an upper portion of the casing from the lower portion and elevating the former in the well bore to a position above the formation Zone, after which the upper portion is cemented in place. After these operations have been completed and the upper and lower stages of cement have set and hardened, the internal mechanism in the upper portion of the casing is drilled out, the drill bit then being lowered through the producing zone and into the lower portion to also drill out its internal mechanism, leaving the upper vand lower portions -with a substantially unobstructed bore.

An object of the present invention is to provide an improved apparatus for releasably interconnecting the upper and lower portions of the well casing, disconnection being effected without the need for rotating the upper portion, which lmight inadvertently rotate the lower portion and adversely affect the cement previously deposited therearound. Disconnection is effected without moving the well casing, and, preferably, by the use of hydraulic pressure.

Another object of the invention is to provide an apparatus for releasably interconnecting the upper and lower portions `of a well casing, in which the lower portion can be cemented in the well bore and any excess cement at the upper end of the upper portion circulated out of the well bore before disconnection between the upper and lower portions is effected, thereby insuring against the presence of cement along the producing Zone above the lower portion, preventing the cement from interfering with the subsequent disconnection of the upper portion from the lower portion, and insuring against cement dropping into the interior of the lower casing portion following the disconnecting action and elevation of the upper portion from the lower portion.

A further object of the invention is to provide an apparatus for releasably interconnecting upper and lower casing sections and for effecting release hydraulically, in which the operator at the tcp of the well bore is given a positive indication that the apparatus is conditioned for hydraulic release by the application of pressure to the fluid in the casing.

An additional object of the invention is to provide an apparatus for releasably interconnecting upper and lower casing sections, the apparatus being of increased strength so as to insure against its being damaged under the action of a drill bit when the internal mechanism in the casing sections are being drilled out, following the cementing of such sections in the well bore.

Another object of the invention is to provide an appa- 3,2%,948 Patented Sept. I4, 11965 ratus for releasably interconnecting upper and lower casing sections, which is comparatively simple, economical to manufacture, structurally strong and sturdy, and easy to operate.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of .a form in which it may be ernbodied. This form is shown in the drawings accompanying and forming part of the present specication. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such ldetailed description is not to be taken in a limiting sense, since the scope `of the invention is best defined by the appended claims.

Referring to the drawings:

FIGURE 1 is a diagrammatic view of an apparatus disposed in a well bore, with its parts in their initial condition preparatory to cementing the lower portion of the casing in place;

FIG. 2 is a view similar to FIG. 1 illustrating the lower portion of the casing cemented in place, the excess cement having been circulated from the well bore;

FIG. 3 is a View similar t-o FIG. 1 illustrating the upper portion of the casing disconnected lfrom the lower portion;

FG. 4 is a view similar to FIG. 1 illustrating the upper portion of the casing elevated a desired distance above the lower portion, with the upper portion cemented in place;

FIGS. 5 and 5a together constitute an enlarged longitudinal section and side elevational view of the apparatus, with the parts in their relative positions disclosed in FIG. l, FIG. 5a constituting a lower continuation of FIG. 5;

FIG. 6 is a view on a reduced scale, similar to FIGS. 5 and 5u, illustrating the apparatus after the upper portion has been released from the lower portion.

As illustrated in the drawings, a well bore A has been drilled through a producing zone P, and it is desired to cement a string of well casing C in the well bore below the producing zone and also above the producing zone, leaving the producing zone itself free from cement. The upper portion D of the casing string is releasably connected to the lower portion E of the casing string by means of a releasing apparatus or disconnectable coupling F, `such upper and lower portions having substantially the same internal diameters.

The releasable apparatus F includes an outer tubular structure 1li comprising a lower Collar 11 threadedly secured to a coupling 12 threaded onto the lower portion vE of the casing string, which terminates in a casing shoe 13 having a central passage 14 therein communicating with a plurality of side ports 15. The internal diameter of the collar 11 is substantially the same as that or" the lower portion E of the casing string. As shown, the rounded nose or guide 16 of the shoe is blank and rests upon and closes a -rat hole G of smaller diameter than the well bore A. Fluids pumped down the casing string C can pass through the shoe passage 14 and out through the side ports 15 for upward movement around the exterior of the Casing string. Return flow of such uid through the side ports and into the lower portion E of the casing string may be prevented by a suitable back pressure valve, such as a fiapper Valve 17 pivotally mounted on the body of the shoe and movable upwardly against a companion seat 18 surrounding the central shoe passage 14.

The outer tubular lmember 10 also includes an outer sleeve 19, the lower end of which is threaded onto the collar 11 and which has an upper tapered guide surface 20 inclined in a downward and inward direction. The sleeve 19 forms a Circumferentially continuous internal groove 21 with the upper end of the collar 11, the

a upper side 22 of the groove providing a cam surface because of its upward and inward inclination. Below the groove 21, the collar has a counterbore 23, the base 24 of which.provides an upwardly facing shoulder.

The inner portion of the disconnectable coupling or releasable apparatus F includes an upper, inner sleeve or tubular member 25, the lower end of which is piloted within the outer tubular member 10, extending along the outer sleeve 19 and the circumferential groove 21, its lower end being disposed within the counterbore 23 and adjacent to the base or shoulder 24 ofthe latter. This inner sleeve or tubular member 25 has a plurality of circumferentially spaced arcuate slots or openings 26 extending vtherethrough containing arcuate keys or dogs 27 which project initially into the lock groove 2li of the outer tubular member. The upper ends 28 of these keys or dogs have cam surfaces companion to the upper side 22 of theg roove, being engageable therewith. When the keys 27 are disposed fully in the groove 21, their inner surfaces 29 conform to the inner surface 30 of the inner sleeve 25, the keys being held in the lock groove by an inner retainer or holding sleeve 31 disposed across the keys, this sleeve being held in such position by a plurality of shear screws 32 threaded in radial holes 33 in the inner tubular member and extending into a peripheral groove 34 in the holding sleeve. Leakage of luid between the inner and outer tubular members 25, 10 is prevented by a suitable seal ring 35, such as a rubber or rubber-like O ring, disposed in an internal groove 36 in the outer member 10 and sealingly engaging against the periphery of the inner tubular member 25. Leakage of uid between the holding sleev 31 and the outer tubular member l is prevented by a suitable seal ring 37, such as a rubber or rubber-like O ring, disposed in a peripheral groove 38 in the holding sleeve and engaging the inner wall of the collar.

When the shear screws 32 are intact, the keys 2'7 are held in their arcuate slots 26 and Within the groove 21, thereby coupling the inner and outer tubular members 10, 25 to one another. Any downward thrust of the inner tubular member 25 on the outer tubular member 1) is transmitted through the lower end of the inner member to the base or shoulder 24 of the counterbore 23. Any upward strain on the inner tubular member 25 is transmitted through the keys 27 to the outer sleeve portion 19 of the outer tubular member.

The inner tubular member 25 forms the lower terminus I of the upper portion D of thec asing string and has substantially the same internal diameter as the collar 1l. Its upper threaded pin 39 is threadedly secured to a coupling 40 threaded to an adjacent casing section of the casing string D, the latter extending to the top of the well bore. The inner tubular member 25 also functions as a cementing device by means of which the upper portion D of the casing string can be cemented in place above the producing formation or zone P. As disclosed,

the inner tubular member 25 is provided with a plurality of side ports 41 closed initially by an inner sleeve valve 42 having a central passage 43 therethrough of a greater internal diameter than the central passage 44 through the holding'sleeve 31. This sleeve valve 42 is held initially in its port closing position by one or more shear screws 45 threaded in the inner tubular member 25 and extending into a peripheral groove 46 in the inner sleeve valve 42. With the shear screws 45 intact, leakage of fluid between the inner sleeve valve 42 and the tubular member 25 is prevented by suitable side seals 47 mounted on the exterior of the inner sleeve valve and engaging the inner wall 30 of the tubular member on opposite sides of the ports 41.

The tubular member 25 also carries a cementing basket 48 whichis initially in a retracted position and which, when expanded, will act as a bridge or barrier to prevent the cement slurry discharged through the .side ports from dropping downwardly along the producing zone P, as

described hereinbelow. The details of construction of the cementing basket and the manner in which it is retained initially in retracted position do not form part of the present invention, and may be found in United States Patent No. 2,602,511, to which attention is directed. In general, the cernenting basket 48 includes a lower sleeve structure 49 mounted on the exterior of the innerk tubular member 25, its downward movement therealong being prevented by a lower stop ring Sil secured to the tubular member by screws 5l, and its upward movement being limited by its engagement with an upper stop ring 52 suitably welded or otherwise secured on the tubular member 25. The cementing basket includes circumferentially spaced longitudinally extending leaf spring members 53 in which a canvas or overlapping metallic leaf structure 54 is disposed, the upper portion of the basket being retained initially in retracted position by an encompassing metallic strap 55 held in constricted position around the upper ends of the leaf springs by a retaining screw 56 extending freely through a hole 57 in the inner tubular member 25 and threaded into the inner sleeve valve 42, which thereby holds the screw head 58 against the ends of the strap. When the screw 56 is disrupted, the strap 55 expands inherently outwardly, allowing the leaf springs 53 and the inner canvas structure 54 to expand and form a bridge or barrier in the well bore, such as illustrated diagrammatically in FIG. 4. Such release occurs as a result of shitting the inner sleeve valve 42 downwardly, which will also open the ports 4l, the inner sleeve valve coming to rest upon a suitable lock screw 59 which is engageable with a lower tooth 60 on the inner sleeve valve 42 to prevent its rotation relative to the inner tubular member 25.

For the purpose of removing excess cement slurry from the well bore surrounding the outer, lower tubular member 10 and also deposited along the producing zone P, a comparatively large side port 61 is provided in the lower tubular member, as through the wall of its collar 11. This side port is initially closed by a blowout plug 62 extending into the port 6l, the plug having an external flange 63 received within a counterbore 64 in the collar, being secured in place by a plurality of screws 65 extending through the plug and threaded into the collar 11. Leakage of fluid around the exterior of the plug 62 is prevented by a suitable side seal 66 engaging the wall of the side port 61.

Below the side port 6la split ring 67 is provided having a substantial arcuate gap 68 between its ends. This ring is threaded in the collar l1 and is adapted to coact with the holding sleeve 3l when the latter is shifted downwardly, as hereinafter described, a tab 69 on the lower end of the holding sleeve entering the gap 68 in the split sleeve and then engaging the latter so that the holding sleeve 31 cannot rotate relative to the ring 67 and the CO1- lar l1, as when the elements internally ofthe collar 11 are to be drilled out following the completion of the upper and lower stage cementing operations.

The casing string C is assembled with the casing releasing apparatus F in its coupled condition, as illustrated in FIGS. 5, 5a and FIG. l. The upper inner sleeve valve 42 is disposed across the side ports 4l to close the latter, and also coacts with the retainer screw 56 to hold the upper cementing basket 4S in retracted position. The lower blowout plug 62 is in place, the holding sleeve 31 being held behind the keys 27 by the shear screws 32 in order to couple the inner sleeve or tubular member 25 to the outer tubular member 10. The apparatus is lowered in the well casing until the lower shoe 13 has reached the bottom of the well bore or the rat hole G, as specifically illustrated in the drawings, or any other desired position in the well bore. As a specific example, the casing string C with the apparatus F mounted thereon may be lowered in the Well bore until the outer tubular member 10 is disposed at the lower end of the producing zone P in the well bore. Circulation may now be established by pumping circulating iluid down through the casing string C, the fluid unseating the back pressure valve 17 and discharging from the side ports for upward passage through the annulus around the casing string to the top of the hole.

After the well bore has been properly conditioned, a suitable quantity of cement slurry is pumped into the casing string, followed by a top cementing plug '70, which is capable of passing through the upper sleeve valve 42 and also through the holding sleeve 31 without tripping either of them. As an example, the top cementing plug 70 may have rubber wiper rings 71 on its peripheral portion adapted to slidably seal against the inner wall of the casing string C and yet be capable of collapsing inwardly for passage through the several restrictions in the casing string provided by the sleeve valve 42, holding sleeve 31 and the anti-rotational lock ring 67. The cement slurry is pumped down the casing string with the top cementing plug 70 at its upper end until the top cementing plug engages the casing shoe 13, closing the passage 14 through the latter, as shown in FIG. 2, and preventing further downward pumping of iluid through the casing shoe. The engagement of the plug 70 with the shoe will be indicated to the operator at the top of the well bore by a rise in the fluid pressure.

Usually, an excess of cement slurry is used for pumping through the shoe 13 and deposit behind the lower portion E of the casing, this cement slurry rising to some extent above the upper end 2t) of the outer tubular member 10 and even, possibly, partially along the producing zone P. It is desirable to remove the excess cement slurry before the upper portion D of the casing string is disconnected from the lower portion. Accordingly, after the top cementing plug 7@ has engaged the shoe, the pressure of the uid in the casing string C can be increased, such pressure acting on the blowout plug 62 and eventually overcoming the tensile strength of the screws 65, disrupting the latter and blowing the plug outwardly of the passage 61 to fully open the comparatively large side port or passage 61. Circulating uid can now be pumped down the casing string C, discharging through the open side port 61 into the well bore and carrying the cement slurry, and the like, upwardly through the annulus around the outer member lil and casing to the top of the well bore, for suitable disposal (FIG. 2).

It is now desired to release the upper portion D of the casing string from the lower portion E and elevate the former from the latter to a position at the upper end of the producing zone P. Accordingly, a suitable trip plug 80 is allowed to gravitate through the fluid in the Well casing, or such plug may actually be pumped downwardly therethrough since the fluid can pass out through the open port 61 and up through the annulus around the casing string D. The trip plug 80 has a maximum diameter which is less than the internal diameter through the upper inner sleeve valve 42, so that it passes therethrough without disrupting its shear screws 45 and then continues on downwardly into engagement with the holding sleeve 31. The engagement of the trip plug with the holding sleeve, as with an upwardly facing shoulder 81 on the holding sleeve (there being a suitable side seal 82 on the trip plug sealingly engaging the inner wall of the holding sleeve 31), will indicate denitely to the operator that the trip plug has moved into sealing engagement with the sleeve 31, since iluid can no longer be pumped downwardly through the casing string and out through the large open port 61. Accordingly, the pressure of the fluid in the upper portion D of the casing string can now be increased to a suiiicient extent to disrupt the shear screws 32 and shift the holding sleeve 31 downwardly into engagement with the anti-rotational lock ring 67, the sleeve moving below the keys or lugs 27. An upward strain can now be taken on the upper portion D of the casing string, which will force the keys 27 upwardly against the cam shoulder 22 of the outer tubular member 10, which will force the keys inwardly through the arcuate slots or openings 26, whereupon they will drop downwardly on top of the holding sleeve 31 and plug 80. The upper portion D of the casing string has now been disconnected from the lower portion E of the casing string, allowing the former to be elevated in the well bore (FIG. 3) to a position in which the inner tubular member 25 is disposed at the upper p0rtion of the producing formation or zone P.

If desired, circulating uid can now be pumped down the casing string C to insure the conditioning of the well bore above the formation zone P, after which an upper trip plug 90 of a suitable type is allowed to gravitate through the casing string, or is pumped downwardly therethrough, this plug being adapted to seal against the interior of the inner sleeve valve 42, coming to rest upon its upper end or shoulder 91. When the trip plug 90 engages inner sleeve valve 42, this factor is indicated to the operator by inability to pump further fluid down the casing string. Accordingly, the pressure of the uid in the latter can be increased to a sufficient extent to disrupt the shear screws 45 and also the retaining screw 56, the sleeve 42 and trip plug 90 moving downwardly until the sleeve engages the stop or lock screw 59, at which time the sleeve 42 is below the opened side ports 41 of the inner tubular member 25. The disruption of the retainer screw 56 allows the latter to be shifted outwardly by the expanding strap 55, the latter being freed from the upper ends of the leaf springs 53 of the basket 48, the basket then expanding outwardly into engagement with the formation above the producing zone P (FIG. 4). A suitable charge of cement slurry can then be pumped down the casing string D, discharging through the open ports 41 and passing upwardly through the annulus between the casing string D and the wall of the well bore A. The expanded basket 48 provides an annular barrier preventing the cement slurry from dropping downwardly along the producing Zone P and contaminating the latter.

After the cement discharged behind the lower portion E of the casing string and the upper portion D of the casing string has set and hardened, the internal mechanism through the casing string can be drilled out by lowering a suitable drill bit on a drill string (not shown) and rotating the bit upon its reaching any obstructions in the well casing. The drill bit can readily disintegrate the upper trip plug 9th and upper sleeve 42, which are made of readily drillable material, such as magnesium. The lock screw 59 prevents the sleeve valve 42 from rotating, insuring its rapid disintegration under the action of the drill bit. The cuttings are circulated out of the hole in a known manner. After the inner sleeve valve 42 and upper trip plug 90 have been disintegrated, the drill bit is moved downwardly into engagement with the lower trip plug and the holding sleeve 31, which are made of readily drillable material, which is also true of the antirotational lock ring 67, the latter preventing the holding sleeve 31 from rotating. Accordingly, rotation of the drill bit and the imposition of appropriate drilling weight thereon will eiect a disintegration of the holding sleeve 31, the lower trip plug 80, and the lock ring 67, the cuttings being circulated out of the hole. The drill bit can now move downwwardly into engagement with the top plug 70 and internal portions of the shoe (which is only shown diagrammatically in the drawings), the internal portions of which are ordinarily made of readily drillable material, the internal mechanism being drilled out so that there is an open passage therethrough communicating with the rat hole G.

Following the drilling out of all the internal mechanism, the drill bit is removed from the well bore and appropriate apparatus can be lowered in the well bore for obtaining production from the formation zone P between the upper and lower casing portions D, E, or from a zone in the rat hole G as well, if it is productive.

With the apparatus F illustrated and described, disconnection between the upper and lower casing portions D, E is effected without the necessity for rotating or otherwise shifting the upper portion D of the casing from the lower portion E. It is merely necessary to apply hydraulic pressure to the mechanism to release the holding sleeve 31 from the keys 2'7, whereupon the mere act of elevating the upper portion D of the casing string will cause the dogs 27 to be cammed inwardly to a released position. Before release occurs, excess cement slurry can be circulated out of the hole so that none of the slurry is present for dropping into the lower casing section E. During the drilling out operation, the drill bit will readily enter the lower portion E of the casing .string and cannot damage the outer tubular member 10 of the latter, since it has substantial wall thicknesses and no openings therethrough. The circumferential lock groove 21 is formed on the interior only of the outer sleeve portion 19 of the outer tubular member 10. It does not extend therethrough. Such portion is of strong and sturdy construction, in view of the lack of any openings therethrough. The only part requiring a milling action is the lower end of the inner tubular member 25, in which the arcuate slots or openings 26 are formed by use of a milling tool. The keys 27 themselves are of extensive arcuate extent and sturdy, but yet are relatively simple, since they can easily be turned as a ring on a lathe and then cut to their required segmental length. The construction of the releasable apparatus Fis such that it can be formed easily and economically, and yet 'oe strong and sturdy. The presence of the large side port 61 not only enables the excess cement slurry from the lower stage cementing operation to be circulated out of the well bore, but also provides the operator with a positive pressure indication that the lower trip plug 80 has reached the holding sleeve 31, so that the appropriate pressure can be applied thereto to effect its downward shifting and its release from its holding position behind the keys or lugs 27.

I claim:

1. In apparatus of the character described: a rst tubular member adapted to be disposed in a well bore; a second tubular member telescopically related to said iirst member, said members having passageway portions in aligned and end-to-end relation of Substantially the same internal diameter; means for releasably coupling said tubular members to one another to permit lowering of said members as a unit in the well bore, comprising a groove in one of said members extending around its entire circumference, the other of said members having a slot; a key in said slot extending into said groove to couple said members together; readily drillable retainer means in the passageway portion of said other of said members shiftable with respect to said other of said members and engaging said key to maintain said key in saidV slot and groove during lowering of said members in the well bore; and means for shifting said retainer means axially out of said other of said members from engaged position with said key and into said one member to allow withdrawal of said key from said groove and disconnection of said members from each other.

2. In apparatus of the character described: an outer tubular member adapted to be disposed in a well bore and having an internal groove extending around its entire circumference; an inner tubular member piloted Within said outer member and having a slot, said members having passageway portions in aligned and end-to-end l relation of substantially the same internal diameter; said tubular members being adapted to be lowered as a unit in the well bore; a key in said slot extending into said groove to couple said members together; readily drillable retainer means in the passageway portion of said inner member shiftable with respect to said inner member and engaging said key to maintain said key in said slot and groove during llowering of said members in the well bore; an-d means for shifting said retainer means axially out of said inner member from engaged position with said key and into said outer member to allow Withdrawal of said 8 l key from said groove and disconnection of said'members from each other.

3. In apparatus of the character described: an outer tubular member adapted to be disposed in a well bore and having an internal groove extending around its entire circumference; an inner tubular member piloted within said outer member and having a slot, said members having passageway portions in aligned and end-toend relation of substantially the same internal diameter; a key in said slot extending into said groove to couple said'members together; readily drillable retainer means in the passageway portion of said inner member shiftable with respect to said inner member and engaging said key to maintain said key -in said slot and groove; and means responsive to the pressure of lluid in said inner tubular member for shifting said retainer means axially out of said inner member from engaged position with said key and into said outer member to allow inward movement of said key from said groove to disconnect said members from each other.

4. In apparatus of the character described: an outer tubular member adapted to be disposed in a well bore and having an internal groove extending around its entire circumference; an inner tubular member piloted within said outer member and having a plurality of circumferentially spaced slots, said members having passageway portions in aligned and end-to-end relation of substantially the same internal diameter; keys in said slots extending into said groove to couple said members together; readily drillable retainer means in the passageway portion of said inner member shiftable with respect to said inner member and engaging said keys to maintain said keys in said slots and groove; and means responsive to the pressure of fluid in said inner tubular member for shifting said retainer means axially out of said inner member from engaged position` with said keys and into said outer member to allow inward movement of said keys from said groove to disconnect said members from each other.

5. In apparatus of the character described: an outer tubular member adapted to be disposed in a well bore and having an internal circumferential groove extending around its circumference and an upwardly facing shoulder below said groove; an inner tubular member piloted in said outer member with the lower end of vsaid inner tubular member adapted to engage said shoulder; said inner member having a passageway portion extending upwardly from its lower end of substantially the same internal diameter as the passageway portion of said outer member extending downwardly from said shoulder; said inner member having a slot in its passageway portion; a key in said slot extending into said groove to couple said members together; retainer means shiftable with respect to said inner member and engaging said key to maintain said key in said slot and groove; and means responsive to the pressure of fluid in said inner tubular member for shifting said retainer means from engaged position with said key to allow inward movement of said key from said groove to disconnect said members from each other.

6. In apparatus of the character described: an outer tubular member adapted to be disposed in a well bore and having an internal circumferential groove extending around its circumference and an upwardly facing shoulder below said groove, the upper end of said outer member tapering in a downward and inward direction; an inner tubular member piloted in said outer member with the lower end of said inner tubular member adapted to engage said shoulder; said inner member having a passageway portion extending upwardly from its lower end cf substantially the same internal diameter as the passageway portion of said outer member extending downwardly from said shoulder; said inner member having a plurality of circumferentially spaced slots in Iits passageway portion; keys in said slots extending into said groove to couple said members together; retainer means shiftable with respect to said inner member and engaging said keys to maintain said keys in said slots and groove; and means responsive to the pressure of fiuid in said inner tubular member for shifting said retainer moans from engaged position with said keys to allow inward movement of said keys from said groove to disconnect said members from each other.

7. In apparatus of the character described: a first tubular member adapted to constitute a lower terminal section of an upper portion of a casing string extending to the-top `of a well bore, said first member having anupper connection for attachment to a section of the casing string thereabove; a second tubular member telescopically related to said first member and adapted to constitute an upper terminal section of a lower portion of the casing string extending downwardly from said first member; said members having an open axial passage therethrough; means for releasably coupling said tubular members to one another when piloted one within the other to permit lowering of said members as a unit in the well bore, comprising .a groove in one of 4said members extending around its entire circumference, the other of said members having a slot; a key in said slot extending into said groove to couple said members together; retainer means shiftable with respect to said other of said members and engaging said key to maintain said key in said slot and groove during lowering of said members in the well bore; means for shifting said retainer means relative to said other of said members from engaged position with said key to allow withdrawal of said key from said groove and disconnection of said members from each other to permit elevation of said first tubular member from said second tubular member; one of said members having a side port below said groove communicating the interior of said one of said members with the well bore externally thereof; releasable means closing said side port and adapted to be released and shifted from said side port to open the same.

8. In apparatus of the character described: an outer tubular member adapted to be disposed in a well bore and having an internal groove extending around its entire circumference; an inner tubular member piloted within said outer member and having la slot; said members having an open axial passage therethrough; one of said members being adapted to constitute a lower terminal section of an upper portion of a casing string extending to the top of the well bore, said one of said members having an upper connection for attachment to a section of the casing string thereabove; said other of said members being adapted to constitute an upper terminal section of a lower portion of the casing string extending downwardly from said one of said members; a key in said slot extending into said groove to couple said members together; retainer means shiftable with respect to said inner member and engaging said key to maintain said key in said slot and groove; means responsive to the pressure of fluid in said inner tubular member for shifting said retainer means from engaged position with said key to allow inward movement of said key from said groove to disconnect said members from each other to permit elevation of said one of said members from said other of said members; one of said members having a side port below said groove communicating the interior of said one of said members with the well bore externally thereof; releasable means closing said side port, said releasable means being responsive to the pressure of fluid in said member to be released and shifted to port opening position.

9. In apparatus of the character described: an outer tubular member adapted to be disposed in a well bore and having an internal circumferential groove extending around its circumference and an upwardly facing shoulder below said groove; an inner tubular member piloted in said outer member with the lower end of said inner tubular member adapted to engage said shoulder; said inner member having a slot; a key in said slot extending into said groove to couple said members together; retainer means shiftable with respect to said inner member and engaging said key to maintain said key in said slot and groove; means responsive to the pressure of fiuid in said inner tubular member for shifting said retainer means from engaged position with said key to allow inward movement of said key from said groove to disconnect said members from each other; said outer member having a side port below said retainer means; a plug closing said port; means releasably securing said plug to said outer member in port closing position, whereby fiuid pressure in said members acting on said plug can release said releasable means and shift said plug from `said port to open the same.

10. In apparatus of the character described: an outer tubular member adapted to be disposed in a well bore and having an internal circumferential groove extending around its circumference and an upwardly facing shoulder below said groove, the upper end of said outer member being tapered in a downward and inward direction; an inner tubular member piloted in said outer member with the lower end of said inner tubular member adapted to engage said shoulder; said inner member having a plurality of circumferentially spaced slots; keys in said `slot extending intoV said groove to couple said members together; a retainer sleeve shiftable with respect to said inner member and engaging said keys to maintain said keys in said slot and groove; means responsive to the pressure of fiuid in said inner tubular member for shifting said sleeve from engaged position with said keys to .allow inward movement of said keys from said groove to disconnect .said members from each other; said outer member having a side port below said sleeve; a plug closing said port; means releasably securing said plug to said outer member in port closing position, whereby iiuid pressure in said members acting on said plug can release Vsaid releasable means and shift said plug from said port to open the same.

11. In apparatus of the character described: an outer tubular member adapted to be disposed in a well bore; an inner tubular member piloted within said outer member; said members having an open axial passage therethrough; one of said members being adapted to constitute a lower terminal section of Ian upper portion of a casing string `extending to the top of the well bore, said one of said members having an upper connection for attachment to a section of the casing string thereabove; said other of said members being adapted to constitute an upper terminal section of a lower portion of the casing string extending downwardly from said one of said members; means comprising a key engaging said members for coupling said members together to permit lowering of said members as a unit in the well bore; retainer means shiftable with respect to said inner member and engaging said key to maintain said key in position coupling said members together during lowering of said members in the well bore; means Ifor shifting said retainer means axially out of said inner member from engaged position with said key and into said outer member to allow release of said key from at least one of said members and disconnection of said members from each other to permit elevation of said one of said members from said other of said members; one of said members having a side port below said key communicating the interior of said one of said members with the well bore externally thereof; .and releasable means closing said side port and adapted to be released and shifted from said side port to open the same.

12. In apparatus of the character described: a first tubular member adapted to be disposed in a well bore; a second tubular member telescopically related to said first member, said members having passageway portions in aligned and end-to-end relation of substantially the same internal diameter; means for releasably coupling said members to one another to permit lowering of said members as a unit in the well bore, comprising a groove in one of said members extending around its entire circumference, the other of said members having 1a slot; a key in said slot extending into said groove to couple said members together; readily drillable retainer means in the passageway portion of said other of said members shiftable with respect to said other of said members and engaging said key to maintain said key in said slot and groove during lowering of said members in the well bore; and means for shifting said retainer means downwardly along and out of Isaid other of said members from engaged position with said key and into said one member to allow withdrawal of said key from said groove and disconnection of said members from each other.

13. In apparatus of the character described: an outer tubular member adapted to be disposed in a well bore and having an internal groove extending around its entire circumference; an inner tubular member piloted within said outer member and having a slot, said members having passageway portions in aligned and end-toend relation of substantially the same internal diameter; said tubular members being adapted to be lowered as a unit in the well bore; a key in said slot extending into said grooveto couple said members together; readily drillable retainer means in the passageway portion of said inner member shiftable with respect to said inner member and engaging said key to maintain said key in said slot and groove during lowering of said members in the well bore; and means for shifting said retainer means downwardly along :and out of said inner member from engaged position with said key and into said outer member to allow withdrawal of said key from said groove and disconnection of said members from each other.

References Cited by the Examiner UNITED STATES PATENTS 2,249,511 7/41 Westall 166--26 X 2,407,983 9/46 Harper 166-27 2,409,811 l0/46 Taylor et ral. 166--125 2,863,511 12/58 M'oosman 166-224 2,953,206 9/60 Brown 166--125 2,950,759 8/ 60 Smith 166--244 X 2,962,096 1'1/ 60 Knox 285-83 X 2,980,185 4/61 Dafn 166-123 X CHARLES E. OCONNELL, Primary Examiner. 

1. IN APPARATUS OF THE CHARACTER DESCRIBED: A FIRST TUBULAR MEMBER ADAPTED TO BE DISPOSED IN A WELL BORE; A SECOND TUBULAR MEMBER TELESCOPICALLY RELATED TO SAID FIRST MEMBER, SAID MEMBERS HAVING PASSAGEWAY PORTIONS IN ALIGNED AND END-TO-END RELATION OF SUBSTANTIALLY THE SAME INTERNAL DIAMETER; MEANS FOR RELEASABLY COUPLING SAID TUBULAR MEMBERS TO ONE ANOTHER TO PERMIT LOWERING OF SAID MEMBERS AS A UNIT IN THE WELL BORE, COMPRISING A GROOVE IN ONE OF SAID MEMBERS EXTENDING AROUND ITS ENTIRE CIRCUMFERENCE, THE OTHER OF SAID MEMBERS HAVING A SLOT; A KEY IN SAID SLOT EXTENDING INTO SAID GROOVE TO COUPLE SAID MEMBERS TOGETHER; READILY DRILLABLE RETAINER MEANS IN THE 